Many people, especially those who reside in cold climates, enjoy having a wood burning fireplace in their homes. Unfortunately, a tremendous degree of manual labor must be expended to provide the requisite firewood associated therewith. Further, the problems associated with lighting the fire, the fire hazard from sparks and the removal of ashes are often disliked by the owners of wood burning fireplaces. As such, a wide variety of gas-fired substitute units have been developed which provide many of the same aesthetic properties of wood burning fireplaces without the concomitant problems.
Typical gas-fired fireplace units normally comprise a natural gas inlet line that leads to a gas manifold located within the firebox of the fireplace. The inlet line passes through the firebox containment bricks or metal liners and will normally include at least one main flow valve and a valved tap for a standing pilot. These valves and any associated electronic controls are placed either in the containment material or within the firebox itself. To complete the unit, a number of simulated, ceramic logs are placed atop the manifold. When the device is lit, flames from the manifold pass upwardly through the logs, thereby simulating the typical flame pattern of a traditional wood burning fireplace.
Although this type of fireplace installation eliminates many of the above-detailed disadvantages of wood burning fireplaces, it suffers from a plethora of problems relative to the lighting and combustion of the gas supply.
In many states, standing pilot lights are being made illegal due to the associated fire hazard. In addition, the standing pilot light is economically unsatisfactory due to its continuous depletion of fuel. One recently employed method of avoiding a standing pilot light has been the addition of a wall switch actuated piezo electric igniter for the pilot, wherein the electronics for the igniter are placed within the firebox containment region. This alleviates the standing pilot problem with newer units that have double wall or similar containment areas that can receive the electronic components. However, there are no similar solutions available for retrofit units that are placed in existing brick fireplaces that do not have double wall or similar construction that can receive the electronic components. By making the electronics part of the fireplace, the prior art also prevents the unit's use as a significant heat source due to the deleterious effect the higher heat output would have on the electronic components. A typical prior art device of this type can produce a heat output on the order of 28,000 BTU's.
Many of the newer gas-fired fireplace units also include an electronically controlled gas inlet valve. This allows a user to simply flip a switch to automatically light the entire unit (both the pilot and the manifold). A problem arises since a fireplace is unlike typical home appliances in that it requires a movable damper in its flue. If a user turns on the unit without first manually opening the damper, a potentially serious and hazardous overheating condition can result since the combustion gases cannot escape up through the flue.